1. Field
This document relates to a flat panel display, and more particularly, to electrically compensating for display defects resulting from process error.
2. Related Art
Flat panel displays include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), an organic light-emitting diode display (OLED), etc. Most of them have been commercialized and came into the market.
Recently, in order to compensate for display defects found in a process of testing a flat panel display, methods of modulating digital video data to be displayed in a display defect area and driving a flat display panel based on the modulated digital video data are being proposed.
Display defects may comprise display spots, bright lines caused by backlight, point defects caused by defective pixels, etc.
The display spot may have a regular shape, such as a point, a line, a belt, a circle, and a polygon, or an irregular shape depending on a cause of occurrence thereof. An area where the display spot is generated has a different color and luminance from those of a normal display surface. The display spot results from a difference in the height of a spacer, parasitic capacitance between signal wirings, parasitic capacitance between a signal wiring and a pixel electrode, an overlap area between the gate and drain of a thin film transistor (hereinafter referred to as a ‘TFT’) due to a difference between an overlap exposure and the amount of exposure caused by lens aberration, and so on as compared with a normal display surface.
The bright line caused by a backlight is a display defect which may occur in a variety of flat panel displays, in particular, a liquid crystal display. In the liquid crystal display, a backlight is placed in the rear surface of a display panel, and light transmissivity from the rear surface of the display panel to the front surface thereof is controlled. Accordingly, if, in the liquid crystal display, light emitting from the backlight is not uniformly incident on the entire incident surface of the display panel, bright lines appear on the display screen.
The point defect caused by a defective pixel is caused by the opening of a signal wiring, a defective TFT, a defective electrode pattern, etc. The point defect caused by a defective pixel results in a dark point or spot in the display screen. Since a spot is conspicuously seen by the naked eye as compared with a dark point, a defective pixel appearing as a spot is processed into a dark point in a conventional repair process. The dark pointed defective pixel is rarely recognized in a black gray level display screen, but is conspicuously recognized as a dark point in display images having an intermediate gray level and a white gray level.
In order to compensate for a display defect, in a conventional method of compensating for display defects of a flat panel display, as shown in FIG. 1, a display defect area within a display panel is designated at step S10, different test data for respective gray levels is displayed in the display defect area at step S20, and compensation data for each gray level is extracted for a display state of the test data through an electrical test using a camera, examination with the naked eye or both at step S30. After the compensation data for each gray level, together with position data to indicate the position of each pixel within the display defect, is stored in memory, display defects are removed through a compensation process using the compensation data at step S50.
However, the conventional method of compensating for display defects of a flat panel display has the following problems.
First, in the conventional method of compensating for display defects of a flat panel display, compensation data for all gray levels is detected. Accordingly, the process time taken to detect the compensation data is long, and memory having a high capacity is required in order to apply the compensation data to an actual display panel. Consequently, this method is disadvantageous in terms of the time and cost.
Second, in the conventional method of compensating for display defects of a flat panel display, compensation data for all gray levels is detected. Accordingly, if compensation data obtained under different conditions for respective gray levels is reflected on consecutive gray level screens, there is a high probability that distorted compensation may be performed. A display defect has a different degree of distribution for each gray level. Here, if the prevision and accuracy in detection for each gray level using a camera is low, the above problem becomes worse at the boundary face of neighboring gray levels.
Third, compensation data is weak against noise when it is actually applied to a display panel. The conventional compensation method requires an additional processor for eliminating this noise.